Use rewrite rules for plugin's custom php page

Hi,

I would like to use rewrite API of WP for my plugin custom php page. I have an order form passing one variable via POST to custom php file (with loaded WP features via the included wp-load.php ) which then do the rest of ordering process.

The problem is, that the url of this order page is not nice (it includes the whole path to this php file). Is there a way how to rewrite it to the nice one?

For example instead of ‘http://www.mypage.com/wp-includes/plugins/my-plugin/order.php’ I want to show ‘http://www.mypage.com/order’.

Thanks for any advice.